1. Field of the Invention
The present invention relates generally to elongated coiled springs for use as plumbers snakes and more particularly to a plumbers snake of novel construction which uniquely optimizes rigidity and flexibility, and to the method of making such a snake.
2. Discussion of the Prior Art
A common type of plumbers snake comprises an elongated coil spring formed of hard drawn wire. The spring is wound tightly generally in a left hand direction so that the coils are in close proximity and resist unwinding when the snake is rotated in a right hand direction within a waste pipe or the like to clear obstructions therein. Under certain operating conditions, these types of springs prove to be too flexible and therefore certain manufacturers provide a metal core to stiffen and strengthen the snake. This latter type of snake has the disadvantage, however, that it has a tendency to assume a permanent set when it is left coiled for any length of time. Further, snakes of this construction are difficult to use in many applications such as around 90.degree. elbows and traps since they lack the required degree of flexibility. Additionally, such snakes tend to kink during operation rendering them unfit for use with the conventional tools employed.
In an attempt to optimize rigidity and flexibility, certain prior art plumbers snakes were provided with a composite core of plastic and metal materials. One of the most successful of these types of devices is described in U.S. Pat. No. 3,149,480 issued to Hunt. This latter device embodies a core of twisted wire strands held centered with respect to an outer coiled spring member by means of an intermediate body formed of a resilient plastic or rubber material. In practice, these devices have proven clearly superior to the prior art all-steel snakes, but still lack the optimum combination of rigidity and flexibility in that for certain applications, greater rigidity is needed. If additional steel wire is added to the core to increase rigidity, however, the desired flexibility is lost.
As will become clear from the discussion which follows, the device of the present invention provides optimum rigidity without sacrificing flexibility. This is accomplished by a unique construction in which right or left hand wound spaced apart spring steel coils formed of oil tempered wire are separated by compressible coils formed of a low density yieldable plastic or rubber material. The compressible coils which separate the steel coils are integral with a generally cylindrically shaped intermediate body formed of yieldable material axially disposed within the interior of the steel coils and surrounding a coaxially aligned metal core constructed of strands of wire. With this novel construction, when the coil spring or snake is bent or flexed, the compressible coils act as a support to the steel coils thereby providing greater rigidity. Because the compressible coils are formed of a resilient, yieldable material, however, the snake remains flexible along its length so that it will easily traverse 90.degree. turns, traps and the like.
In addition to the optimized rigidity and flexibility of the snake of the present invention, it is less expensive to manufacture since less steel is used in coiling. Also, an an added by-product of the unique construction, the yieldable material disposed between the steel coils protects the steel coils against corrosion and wear thereby substantially increasing the useful life of the device.